What you get is what you believe: Eighteen-month-olds demonstrate belief understanding in an unexpected-identity task

• Eighteen-month-olds simultaneously hold two representations of one object.
• They infer another person’s goal based on her belief about the object’s identity.
• They generalize the person’s representations to novel items of the same category.
• Consequently, infants actively help this person accordingly.
• No context information is given, and infants pass from the first trial onwards.

Based on recent findings of implicit studies, researchers have claimed that even infants can understand others’ false beliefs. However, it is unclear whether infants are able to understand others’ belief about an object’s identity when this object can be represented in different ways. In a novel interactive unexpected-identity task derived from the appearance–reality paradigm, 18-month-olds helped an adult to achieve her goal based on the adult’s belief about an object’s identity. To do so, they needed to understand how this adult represented this object—according to its appearance or its real identity—and to generalize these representations to a category of objects. The results suggest that infants’ false-belief understanding is as sophisticated as that of preschool children.